BlockInputStreams StorageSystemTables::read(
const Names & column_names,
const SelectQueryInfo & query_info,
const Context & context,
QueryProcessingStage::Enum /*processed_stage*/,
const size_t max_block_size,
const unsigned /*num_streams*/)
{
check(column_names);
/// Create a mask of what columns are needed in the result.
NameSet names_set(column_names.begin(), column_names.end());
Block sample_block = getSampleBlock();
Block res_block;
std::vector<UInt8> columns_mask(sample_block.columns());
for (size_t i = 0, size = columns_mask.size(); i < size; ++i)
{
if (names_set.count(sample_block.getByPosition(i).name))
{
columns_mask[i] = 1;
res_block.insert(sample_block.getByPosition(i));
}
}
ColumnPtr filtered_databases_column = getFilteredDatabases(query_info.query, context);
return {std::make_shared<TablesBlockInputStream>(
std::move(columns_mask), std::move(res_block), max_block_size, std::move(filtered_databases_column), context)};
}
BlockInputStreams StorageSystemTables::read(
const Names & column_names,
ASTPtr query,
const Context & context,
const Settings & settings,
QueryProcessingStage::Enum & processed_stage,
const size_t max_block_size,
const unsigned threads)
{
check(column_names);
processed_stage = QueryProcessingStage::FetchColumns;
Block block;
ColumnWithTypeAndName col_db;
col_db.name = "database";
col_db.type = std::make_shared<DataTypeString>();
col_db.column = std::make_shared<ColumnString>();
block.insert(col_db);
ColumnWithTypeAndName col_name;
col_name.name = "name";
col_name.type = std::make_shared<DataTypeString>();
col_name.column = std::make_shared<ColumnString>();
block.insert(col_name);
ColumnWithTypeAndName col_engine;
col_engine.name = "engine";
col_engine.type = std::make_shared<DataTypeString>();
col_engine.column = std::make_shared<ColumnString>();
block.insert(col_engine);
ColumnWithTypeAndName filtered_databases_column = getFilteredDatabases(query, context);
for (size_t row_number = 0; row_number < filtered_databases_column.column->size(); ++row_number)
{
std::string database_name = filtered_databases_column.column->getDataAt(row_number).toString();
auto database = context.tryGetDatabase(database_name);
if (!database)
{
/// Базу данных только что удалили.
continue;
}
for (auto iterator = database->getIterator(); iterator->isValid(); iterator->next())
{
col_db.column->insert(database_name);
col_name.column->insert(iterator->name());
col_engine.column->insert(iterator->table()->getName());
}
}
return BlockInputStreams(1, std::make_shared<OneBlockInputStream>(block));
}
